Morphometric analysis of the human superficial radial nerve

The superficial radial nerve (SRN) is one of the cutaneous nerves biopsied for diagnosis of peripheral neuropathy. Morphometric analysis is employed to provide more quantitative data regarding the histomorphology of nerve biopsy. To detect early structural changes, morphometric data from normal nerves are necessary for diagnostic criteria. Unlike the sural nerve, morphometric data on the normal SRN have not been reported. Therefore, a morphometric analysis of the normal human SRN was done in this study. The nerves were harvested bilaterally from 21 fresh human bodies, yielding 34 nerves after excluding damaged ones. Transverse semi-thin sections were analyzed for the number of fascicles, myelinated fiber and axon diameters, myelin sheath thickness, g ratio, density and total number of myelinated fibers using the three-window sampling method. We found that 2–16 fascicles were present. Mean fiber and axon diameters were 6.32 ± 0.09 (SEM) and 3.44 ± 0.06 μm, respectively. Average myelin thickness was 1.44 ± 0.03 μm. Average g ratio was 0.56 ± 0.01. Mean density of fibers was 8,872.9 ± 167.4/mm². The number of fibers varied from 1,390 to 10,941, with an average of 6,495 ± 474. These parameters were independent of age. Asymmetry in the number of fibers was also noted in four cases. The data obtained in this study can be applied to histomorphometric evaluations of SRN biopsies, although the possibility of asymmetry should be considered.     

Connection types between the spinal root of the accessory nerve and the posterior roots of the C2–C6 spinal nerves

Purpose  The aim of this study was to demonstrate the connection types and frequency between the accessory nerve and the posterior roots of the C2–C6 cervical nerves. Methods  The cranial cervical regions of 49 specimens from 27 human cadavers were used for the present study under an operating microscope. Results  Five different connection types between the accessory nerve and the posterior roots of the cervical nerves were recorded and photographed (types A–F). One of these types was not described previously in literature (type F). All connections between the posterior roots of the C2–C6 spinal nerves and the accessory nerve were at the level of the C2 segment. Type B was the most frequently seen type in our series. One of the rootlets of the cervical posterior root joined the accessory nerve without a connection to the spinal cord in type B. Conclusions  The clinical importance of these connections is especially noticed during the radical neck dissection as it may lead to the development of the shoulder-arm syndrome.     

Morphine-sensitive late components of the flexion reflex in the neonatal rat

The 8-15-day-old rat spinal cord was isolated together with peripheral nerves innervating a hindlimb. Multiunit neural discharges in response to electrical stimulation of a cutaneous nerve (sural, plantar of superficial peroneal nerve) were recorded from a flexor nerve (deep peroneal nerve or nerve innervating the hamstring muscles). Attempts were made to find relations between the magnitude of the flexion reflex discharges and the sizes of the volleys in the myelinated or unmyelinated afferent fibers. The neonatal flexion reflex discharges due to myelinated fiber volleys were exaggerated when compared with those in the adult rats. Higher stimulus strengths recruited later components of the flexion reflex discharges. The observed increment of the flexion reflex discharges was precisely associated with the recruitment of unmyelinated afferent fibers in the nerve. These late flexion reflex discharges were shown to be depressed by the opiate analgesic morphine in a naloxone-reversible manner.     

颈椎脊神经沟内口和颈神经的观测

目的　探讨颈椎脊神经沟内口与颈神经受嵌压的关系。方法　取 2 0具成人尸体的颈椎标本 ,选用完整的成人颈椎 4 4套 ,测量颈椎脊神经沟内口的宽度和颈神经穿过脊神经沟内口时的横径 ,并统计两者之间的比值。结果　颈神经穿过脊神经沟内口处的横径为 :C3 为 2 .7± 0 .7mm ,C42 .7± 0 .7mm ,C5为 2 .8± 0 .8mm ,C64.8± 0 .9mm ,C75 .3± 1.1mm。脊神经沟内口的宽度分别为 :C3 为 5 .8± 1.0mm ,C45 .5± 0 .9mm ,C55 .6± 1.0mm ,C65 .5± 1.1mm ,C76 .2± 1.0mm ;颈神经穿过脊神经沟内口时的横径与脊神经沟内口宽度的比值 :C3 为 1∶2 .15 ,C41∶2 .0 5 ,C51∶1.98,C61∶1.14 ,C71∶1.18。结论　脊神经沟内口与穿过内口的颈神经受累关系密切 ,下颈段 (C6、C7)颈神经受累的机率大于上颈段 (C3 、C4)。     

Distribution of myelinated nerves in ascending nerves and myenteric plexus of cat colon

The parts of the colon differ in motor function and in responses to extrinsic and intrinsic nerve stimulation. The distribution of myelinated nerve fibers in the colonic myenteric plexus is not known. Because these fibers might be largely extrinsic in origin, their distribution might indicate the domain of influence of extrinsic nerves and help to explain the different behaviors of the different parts of the colon. Myelinated fibers were examined by electron microscopy in cross sections of the ascending nerves and in myelin-stained whole-mount preparations in the colon. The ascending nerves are much like one another. They have the structure of peripheral nerves, not that of myenteric plexus. The proportion of myelinated fibers in the ascending nerves declines rostrad with no uniform change in total nerve fiber number. Cross-sectional areas of ascending nerves, 3,304 to 7,448 μm²; total number of nerve fibers per profile, 703–2,651; and mean myelin coat thickness, 0.45 ± 0.01 μm, do not change uniformly along the ascending nerves. Myelinated fibers are about 2% of total fibers in the extramural colonic nerves, 7–9% in the ascending nerves in the sigmoid colon, and 2–3% at the rostrad ends of the ascending nerves in the transverse colon. Blood vessels lie at the core of each ascending nerve and on the nerve sheath. Myelinated fibers in the ascending nerves degenerate after section of colonic branches of the pelvic plexus and after section of the pudendal nerves, indicating that myelinated nerves reach the colon through both pathways. Myelinated fibers extend into the myenteric plexus through short lateral branches from the ascending nerves to adjacent ganglia where they turn to run cephalad throughout most of the colon but caudad in the rectum. Myelinated fibers do not extend into the cecum or proximal ascending colon. The nonuniform distribution of myelinated fibers along the colon, many of which are extrinsic in origin, could in part explain the disturbances in defecation that sometimes follow limited distal colonic resection, gynecologic surgery, and obstetric damage to the pudendal nerves in man.     

Anatomical study and clinical significance of the rami communicantes between cervicothoracic ganglion and brachial plexus

The aim of this study was to provide a detailed characterization of the rami communicantes between the stellate (or cervicothoraic) ganglion (CTG) and brachial plexus (BP). Rami communicantes of 33 fixed adult cadavers were macroscopically observed, and connection between CTG and spinal nerves and branching was investigated. In all cases, except one, the hibateral medial rami communicantes was found to be positioned symmetrically between the CTG and C7, C8 spinal nerves. Gray rami communicantes arising from the CTG joined C8, C7, C6 nerve roots on 66, 63, and 6 sides, respectively, and branched from the rami communicantes to C7, C6, C5 nerve roots lying on 51, 41, and 2 sides, respectively. Forty‐five sides of the branches from rami communicantes derived from CTG to C8 were observed to ascend through the transverse foramina of the C7 nerve. The branches from rami communicantes derived from CTG to C7 to the C6 nerve were observed ascending through the foramen transversarium of the six cervical vertebrae along with the vertebral artery and joining the C6 spinal nerve in 41 sides. Knowledge about the general distribution and individual variations of the rami communicantes between CTG and BP will be useful toward studies involving the inference of sympathetic nerve stimulation of the upper limbs and could be important for surgeons who perform surgical procedures in the cervical region or medical blockade of nerve fibers. Clin. Anat. 23:811–814, 2010. © 2010 Wiley‐Liss, Inc.     

Anatomic variation of the spinal origins of lateral and medial pectoral nerves

Lateral and medial pectoral nerves are distributed to the pectoralis major and minor muscles. The purpose of this study was to identify the spinal origins of lateral and medial pectoral nerves and to evaluate the participating amounts of each spinal nerve composing both pectoral nerves. Two types of spinal origins appeared in lateral pectoral nerves. The first type was composed of nerve fibers from C5, C6, and C7 with a frequency of 50.0% and the second type was composed of nerve fibers from C6 and C7 at a frequency of 50.0%. Regarding the average participating diameter to the lateral pectoral nerve, C7 was the thickest with a value of 1.60 +/- 0.35 mm (mean +/- SD), next was C6 at 0.83 +/- 0.18 mm, and C5 was the third at 0.42 +/- 0.24 mm. Three types of spinal origin appeared in the medial pectoral nerve. The first type was comprised of nerve fibers from C8 and T1 in 73.3% of cases. The second type was comprised of C8 only in 23.4% of cases, and the third type was comprised of T1 only in 3.3% of cases. The average participating diameter was 0.71 +/- 0.22 mm from C8 and 0.52 +/- 0.17 mm from T1. These results show that the spinal origins of the both pectoral nerves were various. Participating amounts of the lateral pectoral nerve appeared sequentially in the order of C7, C6, and C5. In the medial pectoral nerve, C8 participated more amounts than T1.     

颈椎脊神经沟及其沟内段脊神经形态学观察

目的　探讨脊神经沟与沟内段脊神经受嵌压的关系。方法　取 6 0具成尸 (男 2 8,女 32 ) 12 0侧颈椎 ,对脊神经沟外口宽度、深度及其沟内段脊神经前支横径进行观察 ,并统计脊神经前支横径与脊神经沟外口宽度之比。结果　①脊神经沟外口宽度、深度自颈 3至颈 6均逐渐增大 ,其平均值分别为 4 5± 1 2mm和4 3± 1 2mm ;② 3到 7颈神经前支横径逐渐增大 ,平均值为 2 9± 1 0mm ;③颈神经前支横径与脊神经沟外口宽度之比 ,颈 5最小 (1∶1 5 4 ) ,颈 4次之 (1∶1 6 7) ,颈 3最大 (1∶1 75 )。结论　脊神经沟与沟内段脊神经受累关系密切 ,下颈段 (5、6 )颈神经受累机率可能大于上颈段 (3、4 )。     

Fiber composition of the rat sciatic nerve

The rat sciatic nerve originates from the spinal segments L4-L6. It is unifascicular at the trochanter; 5-7 mm distally, the nerve splits into two and then into four fascicles. The tibial portion gives rise to the tibial and the sural nerves, and the peroneal portion gives rise to the peroneal nerve and a cutaneous branch that perforates the lateral hamstring muscles to innervate the proximolateral face of the calf. The number and type of the axons in these branches were determined in light and electron micrographs of normal nerves, and after de-efferentation or sympathectomy. Deafferentation was technically not feasible because spinal ganglia and ventral roots were supplied by the same vascular plexus. The tibial nerve contained 1,000 motor and 3,500 myelinated afferent axons, 3,700 sympathetic axons, and 5,400 unmyelinated afferent axons. The peroneal nerve contained 600 motor and 1,300 myelinated afferent axons, 1,100 sympathetic axons and 3,000 unmyelinated afferent axons. The sural nerve contained 1,100 myelinated and 2,800 unmyelinated afferent axons; in addition, there were 1,500 unmyelinated sympathetic axons. The cutaneous branch consisted of 400 myelinated and 1,800 unmyelinated afferent axons. Thus, the entire sciatic nerve at midthigh is composed of about 27,000 axons; 6% are myelinated motor axons, 23% and 48% are myelinated and unmyelinated sensory axons, respectively, and 23% are unmyelinated sympathetic axons. The techniques used did not demonstrate sympathetic axons in the cutaneous branch and did not reveal the few motor axons contained in the sural nerve.     

Anatomical study of the articular branches innervated the hip and knee joint with reference to mechanism of referral pain in hip joint disease patients

Introduction : Referred pain in the anterior knee joint is the most common symptom in hip disease patients. The development of referred pain is considered to be related to dichotomizing peripheral sensory fibers. However, no gross anatomical findings identify any dichotomizing fibers innervating both the hip and knee joints. We dissected the femoral and obturator nerves in human cadavers to investigate the distribution of the articular branches in the hip and knee joints. Fourteen embalmed left lower limbs from 14 Japanese adult cadavers (five from females, nine from males, average age 73.8 ± 14.1 years) were observed macroscopically. The articular branches of the femoral and obturator nerves were dissected at the anterior margin of the groin toward the thigh region. After dissections of the articular nerves of the hip joints, the femoral and obturator nerves were exposed from proximally to distally to identify the articular nerves of the knee joints. The branching pattern of the articular branches in the hip and knee joints was recorded. In six of 14 limbs (42.9%), the femoral nerve supplied articular branches to the anteromedial aspect of both the hip and knee joints. These articular branches were derived from the same bundle of femoral nerve. These gross anatomical findings suggested that dichotomizing peripheral sensory fibers innervate the hip and knee joints and these could relate to the referred pain confirmed in the anterior knee joints of patients with hip disease. Clin. Anat. 31:705–709, 2018. © 2018 Wiley Periodicals, Inc.     

Distribution and Ultrastructure of Afferent Fibers in the Parietal Peritoneum of the Rat

The distribution and the ultrastructure of afferent fibers innervating the parietal peritoneum in the rat was studied with immunohistochemistry using an antiserum against the neuronal marker protein gene product 9.5. The immunoreactive fibers were distributed throughout the peritoneum. They generally ran straight and parallel to the intercostal nerves running in the abdominal muscles underlying the peritoneum. They sometimes branched and terminated by forming club‐like endings. The number of nerve endings on the peritoneal surface was 3.25 ± 1.66 mm^?2. Electron microscopic observations revealed both unmyelinated and myelinated nerve fibers. The unmyelinated fibers were thin and about 1 μm in diameter. Their endings formed slight swellings located just inside the peritoneal cell layer. The myelinated fibers often formed a bundle that was composed of two or three nerve fibers. Each myelinated fiber kept in contact with a Shwann cell and projected toward the peritoneal cavity. Finally, they penetrated the peritoneal cell layer to reach the peritoneal cavity. These fibers then made contacts with the peritoneal cells and became free from the myelin sheath. The ending had a club‐like shape covered with collagen fibers, and contained many neurofilaments, a few mitochondria, but no synaptic vesicles. These results suggest that since the sensory endings are exposed at the peritoneal cavity, the sensory fibers are highly sensitive to somatic or nociceptive stimuli. Anat Rec, 2011. © 2011 Wiley‐Liss, Inc.     

Different patterns in age-related morphometric alteration of myelinated fibers and capillaries of the tibial nerve: a longitudinal study in normal rats

Age-related regression of myelinated fibers in peripheral nerves of the lower limbs is strongly influenced by capillaries and results in balance dysfunction and falls. However, the temporal relationships between alteration patterns of myelinated fibers and capillaries have not yet been clarified. This study aimed to investigate age-related morphological and histological changes of both myelinated fibers and capillaries in peripheral nerves to clarify whether myelinated fibers or capillaries change earlier. Seven male Wistar rats each were randomly selected at 20 weeks (young group), 70 weeks (middle group), and 97 weeks (old group) for histological evaluations. The left and right tibial nerves were removed morphologically and histologically to examine myelinated fibers and capillaries. Axon diameter and myelin thickness were almost unaltered in the middle group compared with the young group but were significantly reduced in the old group when compared with the other two groups. However, the capillary diameter and number of microvascular branch points were substantially reduced in the middle group. The current study demonstrates that myelinated fibers of peripheral nerves show signs of regression in elderly rats, whereas capillaries start to reduce in middle-aged animals. In normal aging of the tibial nerve, capillaries may regress before myelinated fibers.     

Observation and measurements of long thoracic nerve: a cadaver study and clinical consideration

Long thoracic nerve (LTN) is an important nerve originating from cervical nerve roots. It varies a lot in origins and branches, which lead to several clinical problems, such as diagnosis, prophylaxis and treatment of LTN injury. LTN was dissected in 38 cadavers in the present study. Origin, level of union, branches, sites where nerve entered the muscle, length of nerve trunk and branches as well as transverse diameter were documented. Different derivations of LTN were observed, and C4-7, C5-7, C5 and C7, C5-7, C5-8, C6 and C7, and branch from C6 was the most important components of LTN. After evolution, LTN trunk was composed by superior and inferior trunks at scalenus muscle or the three superior slips level. Branches of LTN traveled on the surface of the six superior slips of anterior serratus muscle and then penetrated through the inferior slips without correlation between different branches. Mean length of trunk of LTN is 111.73 (30.08) mm, axis of cross section was 2.27 × 0.96 mm at the union level and 1.91 × 0.68 mm at the end branch. Each slip was innervated by 1–4 branches of LTN. The observation and measurement data described in our study presented some variations and could provide clinicians with important information on diagnosis, prophylaxis and treatment of LTN injury and pursuing more suitable muscle flaps for reconstruction operation.     

Spinal root origins and innervations of the suprascapular nerve

The suprascapular nerve branches provide efferent innervation to the supraspinatus and infraspinatus muscles as well as sensory innervation to the shoulder joint. This study was carried out to verify the spinal root origins and innervations of the suprascapular nerve. Fifty samples of the suprascapular nerve taken from 37 adult Korean cadavers were used in this study. The suprascapular nerve was found to comprise the ventral rami of the C5 and C6 in 76.0% of the fifty samples; C4, C5, and C6 nerves in 18.0%; and C5 nerve in only 6.0%. The C5 nerve was consistently shown to be the largest in mean diameter and was found to be a major contributor of nerve fibers leading to the suprascapular nerve. This study shows that the main spinal component of the suprascapular nerve is C5 nerve. In most cases, the rate of the involvement of the C4 and C6 nerves (18.0 and 94.0%, respectively) with the suprascapular nerve was less than that of C5 nerve. C4 and C5 nerves were shown to contribute nerve fibers to the supraspinatus and infraspinatus muscles and to both shoulder joints, whereas C6 nerve displayed variable patterns of innervation.     

Semiquantifying of fascicles of the C7 spinal nerve in the upper and lower subscapular nerves innervating the subscapularis and its clinical inference in Erb's palsy

To elucidate anatomic basis of susceptibility for contracture of the subscapularis muscle in Erb's palsy of the brachial plexus, we semiquantitatively studied the spinal nerve origins of the subscapular nerves innervating the subscapularis, with special reference to the contribution of C7 innervation to the subscapularis. Thirty‐three sides of formalin‐fixed upper extremities were dissected to obtain the intact brachial plexus. After immersed in 10% acetic acid for 2 weeks, the upper and lower subscapular nerves innervating the whole subscapularis, were dissected retrogradely to verify their spinal nerve origins. The cross‐sectional area by C7 innervation and that by the upper trunk innervation was calculated respectively to obtain the constituent percentage of different components in the upper and lower subscapular nerves. In the upper subscapular nerve, fascicles of C7 accounted for 0% (interquartile range, 0–1.1%) of cross‐sectional area and those of the upper trunk, 100% (98.9–100%). In the lower subscapular nerve, fascicles of C7 accounted for 40.5% (23.5–47.5%) and those of the upper trunk, 59.5% (52.5–76.5%). In total, 18.6% (13.3–27.3%) of fascicles in the subscapular nerves innervating the subscapularis originated from C7, while 81.4% (72.7–86.7%) of those came from the upper trunk. It is confirmed that innervation of the subscapularis originates from more spinal cord segments than that of infraspinatus and teres minor, and this may be the main reason for which in Erb's palsy, functional recovery of the subscapularis is often faster than that of lateral rotators of the shoulder, resulting in medial rotation contracture of the shoulder. Clin. Anat., 2013. © 2012 Wiley Periodicals, Inc.     

The distribution of ganglion cells in the posterior cricoarytenoid muscle of the normal adult rat. A light and electron microscopic study

We employed by light and electron microscopy to examine the innervation of the posterior cricoarytenoid muscle of the adult rat. The laryngeal nerve was found to often bifurcate into two different bundles. One contained large myelinated (motor) nerve fibers, which were located along the frontal (ventral) muscle surface and entered the muscle at its middle portion to form neuromuscular contacts with individual muscle fibers. The other nerve bundle consisting of clustered ganglion cells (20-30 microm in diameter) and their associated nonmyelinated and small-sized myelinated nerve fibers were mainly found on the dorsal side of the muscle and often ran along the peripheral clefts or depressions of the muscle surface. The nerve bundle often extended side branches, which entered the muscle to be distributed among muscle fibers and near arterioles. Some ganglion cells are considered to enter the muscle, accompanied by branched nerves. Intramuscular ganglion cells and their associated nerve fibers examined by electron microscopy were similar in fine structure to perimuscular ganglion cells and their associated nerve fibers. Nerve fibers contained abundant clear synaptic vesicles which were cholinergic in nature, and often formed synapses with both neighboring axons and the cell body of the ganglion cells. These findings suggest that, in the rat posterior cricoarytenoid muscle, perimuscular and intramuscular ganglion cells exist and may be involved in innervating and contracting smooth muscle cells of the arterioles, thus regulating the blood flow or intravascular pressure.     

三角肌神经入肌点定位及肌内神经分布的研究

目的　揭示三角肌神经入肌点和肌内神经分支分布 ,为其临床应用提供较为详尽的形态学资料。方法　①用经甲醛固定 2年以上的成人尸体 (2 0～ 5 0岁 ) 12具 (男 9,女 3)共 2 4侧。以肩峰后角为骨性标志 ,测量三角肌各亚部神经支入肌点的位置。②用经甲醛固定 1年以内的童尸 3具 (3～ 10岁 )及成人尸体 2具 (2 0、4 0岁 )完整取下三角肌 ,采用Sihler′s肌内神经染色法观察肌内神经分支分布。结果　①三角肌各亚部神经入肌点的体表投影 :三角肌前亚部、中亚部、后亚部的神经入肌点分别在距肩峰后角下方 (5 7± 0 7)cm、(5 9± 0 8)cm、(4 8± 0 5 )cm处的水平线上 ,距三角肌前缘外后方 (3 6± 0 4 )cm处及距三角肌后缘外前方 (3 5± 0 6 )cm、(2 3± 0 3)cm处 ,上述三点均在肌的中 1/3部。②肌内神经分布 :三角肌前、后亚部的肌内神经支在肌内为直接横过肌纤维中部 ,沿途再发出分支与肌纤维并行走行 ;而中亚部肌内神经支在各个羽内 ,与肌纤维相交 ,行向短肌纤维的起止端。结论　①三角肌的神经入肌部位及入肌形式与该肌的形态和功能有关联 ;②三角肌的肌内神经分支分布可能与该肌的肌纤维长度及肌纤维型有关 ;③三角肌中亚部的肌内神经吻合网较宽而致密 ,推测有着更精细的神经调节。     

On the organization of the thoracic spinal ganglion and nerve in the rat

Summary The location of spinal ganglion cells projecting into various thoracic spinal nerve branches in the rat has been investigated using retrograde transport of horseradish peroxidase (HRP). In addition, total numbers of myelinated and unmyelinated axons in three consecutive pairs of thoracic spinal nerves have been analyzed. The animals were perfused one to 2 days after application of HRP to thoracic spinal nerve branches and several ipsilateral spinal ganglia sectioned and processed for HRP histochemistry. Labeled cells were found in ganglia corresponding to the level of operation, as well as several adjacent rostrally and caudally located ganglia. No somatotopic organization was found within the ganglia, but occasionally a clustering of labeled cells belonging to the same peripheral nerve was observed. Pieces from three consecutive pairs of ventral and dorsal spinal nerve rami were removed from two normal rats and embedded in Vestopal. Semithin sections including the entire cross-sectional area of the rami were used to count the total number of myelinated axons. The number of unmyelinated axons was estimated by sample counting in the electron microscope. The ventral ramus of the spinal nerve contained about twice as many axons and a lower proportion of unmyelinated fibers in comparison with the dorsal ramus. Large differences in the number of axons between the two sides in pairs of spinal nerve rami and entire spinal nerves were found. These differences diminished when comparing the total number of axons from three consecutive rami or nerves on each side. The results of the present study are compatible with the notion that although there is a strict somatotopic organization of the periphery in the spinal cord dorsal horn, the pathway between these two sites is relatively diffusely organized. It is possible that there is instead a modality-related organization in the peripheral nerve pathway.